What Is Material Balance

Material balance involves making an inventory of the quantities going in and out of a system. These quantities could be as simple as the total mass. The principles of material balances can be expanded to the balance of energy, electrical charge, and virtually any quantity that is conserved. 

Material balance is based on the law of conservation of mass that was established by Antoine Lavoisier (1743-1794) and states that mass can neither be created nor destroyed, but is conserved (in any ordinary chemical reaction). 

In general and simple terms (Fig. 7.6) we can express a total mass balance for a given unit or system as follows  

Total input mass flow rate — Total output mass flow rate = Rate of accumulation [unsteady-state condition]. 

If input and output mass flow rates are equal, then we can say that the unit or system is under steady-state conditions because all mass flow rates and the retention mass of the system remain constant (further analysis and more explanations are given in Sect. 7.4). Therefore  

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What is material balance control for a complete plant In what sense is it different from the set point control we have seen in earlier chapters Discuss the two approaches for the implementation of material balance control. Which one is preferable, implementation in the direction of process flow or opposite to it Elaborate on your answer. Would you use steady-state or dynamic models for material balance control, and why (Note You will find Chapter 13 of Ref. 16 very useful in answering these questions.)... 

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